I used to be a HISTA CM and I'd say it's much less scary than It's Tough to Be a Bug ... at HISTA we'd get maybe one child who needed to leave, every second or third show (compared to 3-4 every single show at ITTBAB).
It has a snake and a lion that "jump out" at you, and the mouse effect, which feels like mice running across your legs. If you keep your DD on your lap, or have her lift up her legs/sit cross-legged when the mice are coming (trust me, you'll know when they're coming long before you actually feel it), then she'll miss that.
In fact, I think all the effects are fairly predictable--like "There's a normal sized snake. Now there's a big snake slithering across the creen. Now there's a big snake centered on the screen. Oh, now it's hissing and snapping at me."
It's certainly less scary than ITTBAB, or Dinosaur, or Star Tours, or the ExtraTERRORestrial Alien Encounter. (Not sure how it compares to Stitch--I'd bet a lot of kids aren't scared of Stitch like they would be if they didn't know the character.) I would probably say it's on par with the Great Movie Ride for scariness? Or maybe Maelstrom or Test Track (minus the thrills).